Sealing mechanism for vertical axis centrifugal pumps



23, 1952 E. MALMVIK SEALING MECHANISM FOR VERTICAL AXIS CENTRIFUGAL PUMPS Filed Aug. 23 1946 3 Sheets-Sheet 1 Dec. 23, 1952 E. MALMVIK 2,622,902

SEALING MECHANISM FOR VERTICAL AXIS CENTRIFUGAL PUMPS Filed Aug. 23, 1946 3 Sheets-Sheet 2 E.- MALMVIK Dec. 23, 1952 SEALING MECHANISM FOR VERTICAL AXIS CENTRIFUGAL PUMPS 5 Sheets-Sheet 5 Filed Aug. 25 1946 Patented Dec. 23, 1952 SEALING MECHANISM FOR VERTICAL AXIS CENTRIFUGAL PUMPS Elof Malmvik, Jonkoping, Sweden, assignor to Jiinkiipings Mekaniska Werkstads Aktiebolag, Jonkoping, Sweden, a joint stock company of Sweden Application August 23, 1946, Serial No. 692,594 In Sweden February 25, 1944 4 Claims. 1

The invention relates to sealing devices for centrifugal pumps of the vertical axis type, the said devices including an hydraulic seal and a ring valve to prevent leakage of the pump fiuid during the operation of the pump as well as when the pump is stopped. sible to dispense with stufling boxes, which have not been durable in connection with pumping of acids and other corrosive liquids, especially if the liquids have a high temperature, as they are damaged in a short time and must be repaired.

One object of the invention is to provide an automatically operating sealing device of such construction that a high efiiciency of the pump is obtained.

Another object of the invention is to prevent the fluid, especially acids which would corrode or otherwise damage the material used for the ring valve, from coming normally in contact with said ring valve.

A further object of the invention is to provide a sealing device which can operate when either an overpressure or a vacuum is present in the intake of the pump.

A still further object of the invention is to secure a reliable operation of the sealing device on starting the pump independently of whether an overpressure or a vacuum is maintained in the part of the pump chamber communicating with the sealing device.

The invention will be more clearly described below, reference being made to the accompanying drawing, in which,

Fig. 1 is an axial section of the sealing device and the ring valve of a vertical pump according to one embodiment of the invention.

Figs. 2 and 3 are axial sections of two modified embodiments of the ring valve.

Fig. 4 is an axial section of the ring valve according to a further modification combined with a trap preventing leakage of gases.

Fig. 5 is an axial section of a vertical pump provided with a sealing device and a ring valve substantially according to Fig. 1.

As shown in Fig. 5 the centrifugal pump is arranged vertically and has no stufiing box. The main pump impeller 26 is provided on the lower end of the vertical shaft I in the pump chamber, and the pump intake 21 is located above the impeller, whereas the lower side of the pump chamber is closed.

A sealing impeller 2 with a lower series of blades or wings 3 and an upper series 4 is secured to the shaft I and rotates in a sealing chamber located at the same side of the pump impeller It is thereby pos- 26 as the intake 21 and thus on the suction side of the pump. From the inner edge of the bottom of the sealing chamber a ring-shaped wall or flange 28 extends upwards so that a pocket is formed, whereby a sufficient sealing liquid always is present in the sealing chamber to provide the sealing action of the impeller 2 on starting the pump.

If the suction pipe is connected to a high liquid container and the container is filled with a liquid such as black liquid, this may result in an overpressure in the intake 21. The liquid then fiows into the sealing chamber through an annular passage around the shaft to the upper portion thereof, Where a sufficient pressure is obtained by the blades 4 to counteract the pressure from the blades 3 and the overpressure in the intake. The rotating liquid thus forms a seal preventing the liquid from passing upwards and out of the sealing chamber. If the liquid level in the container lowered and a vacuum is obtained in the intake 21, liquid in the sealing chamber will fiow back to the pump, but sufficient liquid is maintained by the action of the blades 3 to form a seal preventing air from passing to the pump chamber.

In order to prevent the pump liquid from passing through the sealing chamber on stopping the pump a ring valve is provided above the sealing chamber. According to Figs. 1 and 5 a ring 5 is fixed to the pump casing at its outer edge close to the blades 4, and to this ring is fixed a valve plate comprising a corrugated membrane 6 of acid-proof steel fastened to the ring 5 by means of an upper press ring I and screws 8. At the inner edge, the membrane is provided with a sealing ring 9, located at such a short distance from a valve seat I0 rotating with the shaft that only a sufficient space is obtained to prevent the parts 9 and ill from touching each other during the operation of the pump. When the pump is stopped the pressure of the liquid causes the valve plate to be pressed with the sealing ring 9 against the seat Ill thereby closing the valve. If, however, the ring 9 accidentally should not close entirely, the leaking liquid may be collected and. flow out through the pipe 29 shown in Fig. 5 or the pipe 24 in Fig. 4.

The different parts in the sealing device may be made of acid-proof material, and the ring 9 may have its valve surface covered with rubber, lead or other suitable material. The valve ring 6 may also be made as a plane steel plate in order to withstand a higher pressure. It is also in many cases possible to make the valve ring as a rubber ring I I, as shown in Fig. 2.

According to the embodiment shown in Fig. 3 the valve ring is fastened to the pump shaft and is thus rotating with this shaft. The rubber ring i2 is here inserted with its inner edge between the flange I3 and the pressing plate H but is not perpendicular to the shaft as in Figs. 1 and 2 but forms a less angle than 90, so that its outer edge is located somewhat higher than its inner edge. When the pump is standing still and independently of an over-pressure in the pocket below the valve ring the outer part of this ring rests against the seat forming a ring l5 fastened to the pump casing. On starting the pump the ring is caused by the centrifugal force to be removed a short distance from the ring l5 thereby avoiding Wearing against the ring [5. For obtaining a sufficient great centrifugal force the valve ring It may be provided with an outer steel ring it, and to secure a sufficient tightening pressure springs l1 may be applied.

According to Fig. 4 the pump casing is provided with a member l3 forming a ring-shaped chamber l9 and an upwardly open, ring-shaped channel 2| close to the pump shaft 20, which channel is filled with a liquid, such as oil. Into the oil descends a rotatable and substantially cylindrical wall 22, which is gas-tight fastened to the shaft 25. Close beneath the bottom of the channel 2| are arranged a number of blades 25 on a collet secured to the shaft 20. From the chamber IS a pipe 24 leads to the place at a sufiicient distance, so that gases from the chamber I9 may be allowed to escape through the pipe without inconvenience. To the member i8 is further fastened a ring-shaped steel membrane 23 having its inner edge at a short distance from a corresponding valve seat.

This sealing device operates as follows. During the rotation of the pump wheel gases from the pump liquid may pass to the chamber l9, but within certain limits the trap 2|, 22 tightens reliably. As the wall 22 rotates in the oil this is brought in rotation, and to prevent the oil from flowing out the outer wall of the channel 2| and preferably also the outer surface of the wall 22 are converging upwards, so that the oil by the centrifugal force is pressed downwards. When the blades 25 are rotating, they serve as a ventilator and counter-act an over-pressure in the chamber l9, so that a lower pressure is obtained in the inner part of the trap. If, however, the over-pressure should increase in the chamber l9 so that the oil could be pressed out, this is prevented by the pipe Zt, as only an over-pressure corresponding to the friction in the pipe may be obtained in chamber l9.

In order to ascertain that on stopping the pump the oil be not mixed with the pump liquid or pressed out from the trap by said liquid the valve ring 23 closes automatically the connection with the pump wheel by the increasing pressure.

I claim:

1. A sealing mechanism for a vertical axis centrifugal pump having a casing and a vertical shaft, said sealing device comprising a sealing chamber having an opening at its upper part for the pump shaft, said chamber including a wall extending around the pump shaft in close proximity thereto and extending upwardly from the bottom of the chamber so as to form a pocket for holding pump liquid when the pump is stopped, a. sealing impeller fixed to the shaft in said chamber, said impeller having two sets of blades acting toward each other, one of said sets of blades extending downwardly into said pocket, an elastic ring valve located above said impeller for sealing said opening in said chamber under the influence of pressure of the pump fiuid when the pump is stopped and being biased to open position when the pump is operating, said ring valve being fastened with one of its edges to one of two parts consisting of the pump casing and the pump shaft and extending with its other edge to a position below a valve seat fixed to the other of said two parts.

2. A sealing device for a vertical axis centrifugal pump having a casing and a shaft, comprising a sealing formed with an annular pocket in its lower portion extending around the pump shaft for holding pump fluid when the pump is stopped, a ring valve located at an upper opening of said sealing chamber and adapted to be kept closed by the pressure of the pump liquid when the pump is stopped, and a sealing impeller in said sealing chamber, said ring valve comprising a ring-shaped elastic valve plate around the pump shaft fastened with its outer portion in the pump casing, extending with its inner edge below a valve seat fixed to the pump shaft and keeping by itself the valve open during the operation of the pump, and said sealing impeller being fixed to the shaft below said ring valve and comprising upper and lower sets of blades acting towards each other, the lower set of said blades descending into said annular pocket around the pump shaft.

3. A sealing mechanism for a vertical axis centrifugal pump having a casing and a shaft, comprising a sealing chamber, formed with an annular pocket in its lower portion extending around the pump shaft for holding pump fluid when the pump is stopped, a ring valve located at an upper opening of said sealing chamber and adapted to be kept closed by the pressure of the pump liquid when the pump is stopped and a sealing impeller in said sealing chamber, said ring valve comprising a ring-shaped elastic valve plate around the pump shaft fastened with its inner portion to the shaft and extending with its outer edge below a conical valve seat fixed to the pump casing so as to be removed from said valve seat by the action of the centrifugal force of said valve plate, and said sealing impeller being fixed to the shaft below said ring valve and comprising upper and lower sets of blades acting towards each other, the lower set of said blades descending in a ring-shaped pocket around the pump shaft.

4. A sealing mechanism for a vertical axis centrifugal pump having a casing and a shaft, comprising a sealing chamber, formed with an annular pocket in its lower portion extending around the pump shaft for holding pump fluid when pump is stopped, a ring valve located at an upper opening .of said sealing chamber and, adapted to be kept closed by the pressure of the pump liquid when the pump is stopped, a sealing impeller in said sealing chamber, said ring valve comprising a ring-shaped elastic valve plate around the pump shaft fastened with one of its edges in one of two parts consisting of the pump shaft and the pump casing and extending with its other edge below a valve set fixed to the other part and keeping by itself the valve open during the operation of the pump, said sealing impeller being fixed to the shaft below said ring valve and having upper and lower sets of blades acting towards each other, the lower set of said blades 5 descending in said annular pocket around the pump shaft, a sealing trap located between said ring valve and the outer air and comprising an upwardly open, ring-shaped and stationary channel for a liquid around the pump shaft and a ring-shaped wall fastened to the pump shaft and descending in said channel.

ELOF MALMVIK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date De Bijll Naohenius July 23, 1918 Wilfiey July 20, 1920 Number Number Number 

